PostgreSQL is an object-relational database management system (ORDBMS). It is released under a BSD-style license and is thus free software. PostgreSQL is not controlled by any single company, but relies on a global community of developers and companies to develop it.The mixed-capitalization of the PostgreSQL name can confuse some people on first viewing. The several pronunciations of 'SQL' can lead to this confusion. However, the PostgreSQL Core Team announced in 2007 that the product would continue to be named PostgreSQL. The name refers to the project's origins as a "post-Ingres" database, the original authors having also developed the Ingres database.
PostgreSQL includes built-in support for B+-tree, hash, GiST and GiN indexes. In addition, user-defined index methods can be created, although this is quite an involved process. Indexes in PostgreSQL also support the following features:
*PostgreSQL is capable of scanning indexes backwards when needed; a separate index is never needed to support
ORDER BY field DESC.*Expression indexes can be created with an index of the result of an expression or function, instead of simply the value of a column.
*Partial indexes, which only index part of a table, can be created by adding a
WHERE clause to the end of the CREATE INDEX statement. This allows a smaller index to be created.*The planner is capable of using multiple indexes together to satisfy complex queries, using temporary in-memory bitmap index operations.
**DIFFERENCE BETWEEN MEMORY VARIABLE AND DATABASE FIELD
Memory variable is an attribute of a physical or an abstract system which may change its value while it is under observation while database fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database.
**DIFFERENCE BETWEEN DATABASE RECORD AND DATABASE FIELD
The difference between database field and database record is that, database fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database while database records are organized into tables that include information about relationships between its various fields.
No comments:
Post a Comment